Duplex steam engine



Jan. 8., 1935. M. Wl DOLE 1,987,003

DUPLEX STEAM ENGINE Filed July 13, 1934 2 Sheets-Sheetl D Fi gl.

aa/ 5 G C) 58 E f lnvenToT. 67 Myron W. D016 Jan. s, 1935. M, W. DOLE 1,987,003

DUPLEX STEAM ENGINE Patented Jan. 8, 1935 UNITED stares! 'PATENToFrlcE This invention relates to `'duplex steam engines of the type in which the pistons have no mechanical connection with each other and are, therefore, capable of movement independently of each other, and in which the -pistonreve`rsing means is constructed to maintainv thepiston's' in an out-of-step relation so that rthey Vwill not reverse at the same time. A steam engineof this type is illustrated in my Patentv No. 1,962,986,

June 12, 1934. Such al duplex steam engine is it is desirable that each power piston should make useful for various purposes,V such as operating la duplex double-acting pump .so as to produce a continuous flow, the out-of-step, relation between the pistons resulting in each piston delivering fluid through the discharge of the pump while the other piston is reversing. In the device shown in my above-,mentione patent one of the power pistons is a self-reversing piston, the valve mechanism for the corresponding cylinder being of the usual type which causes piston reversal at each end ofthe stroke automatically by the movementof that piston. The valve mechanism for the other cylinder is constructed so that it causes piston reversal automatically by the operation of its piston at one end of the stroke while atthe other end of the stroke the joint action of said piston andr a valve mechanism controlled by the other or first-named or self-reversing piston-,is necessary to cause piston reversal. l

One of the objects of the present invention is to provideimprovements in valve'mechanism for steam engines of this type by which the devices rendered operative by the self-reversing ypiston to assist in reversing the other piston at one end of its stroke will be operative during a limited kportion only of the stroke of said 4self-reversing piston and will be inoperativel at other portions of the stroke. In other words, the .construction of this invention is such that during a limited portion of the stroke of the self-reversing piston the latter providesthe opportunity for the reversal of the other piston provided it has reached the end of its stroke, such opportunity being removed afterthe self-reversing piston has cornpleted its travel through the predetermined portion of its stroke. y

The valve mechanism illustrated in said patent is of the type in which the steam valve for each cylinder is v actuated by a differential piston mechanism larranged so that when steam is admitted to one end ofthe cylinder of the differential piston said valve will be shifted into one position to admit steam to one end and to exhaust steam from the other end ofthe power end oflthe'differential cylinder the differential piston operates to shift the valve` into position to admit steam to the other end and to exhaust ,steam "from the first-named endv of the DOWQT cylinderand admissionand exhaust of steam to the end 4of the differential cylinder'is determined by a reversing valve which is actuated from the power piston.`

In the voperation of steam engines ofthis type the full complete stroke and ,inl order' that the stroke of each power piston may be completed in one direction yit is necessary that the steam pressure should be maintained in oney end of the differential'cylinder for the steam vvalve during the entire stroke of4 said power piston.

[Another objectof vmy present invention is to reversing even though there' should be leakage of steam from the differential cylinder, this fea'- ture constituting, as it were, a steam-pressureits stroke.

ymaintainingfeature for preventing reversal of the Vsteam'valve until the power piston has completed My present. invention is adaptedfor use in a duplex engine whether the latter be of the simple v type or the compound type and for illustrative purposes` I have shown in thedrawings .the invention as applied Vto both types of engines.

Fig. 1 is a diagrammatic sectional View of a ,duplex steam engine having `simple cylinders and showing a selected embodiment of my invention;

Fig. 2 is4 a sectional view of the valve device which coi-operates with one of the pistons to eiec't the reversal of the other piston at one end of its stroke;v

Fig. Bis a view to a compound engine;

Fig. 4 is a View similar to Fig. 2 but showing similar` to Fig. 1 but showingv one ,way in which the invention may be applied the type of valve andits connections used with 4the compound engine.

Fig. 5 is a fragmentary view looking toward the left in Fig. 2 and showing the check valves 58. In the selected embodiment shown in Fig. 1 the duplex steam engine comprises the two cylpurnp pistons of the duplex pump as usual vices of this type.

cylinder, while when steam is exhausted from said The valve mechanism controlling the admission of steam to the cylinder 1 is of known construction and is-such as is commonly used in steam engines of this type. The steam valve for the cylinder 1 is shown at 6 and it operates in a steam chest 7 which communicates by a passage 8 with a steam supply pipe 9. The cylinder 1 is provided with the two ports 10 and 11 leading from the steam chest '7 to ,the opposite ends of the cylinder 1 and the valve 6 has the usual 'exhaust cavity' 12 which, when the valve 6 is in l the position to uncover the port 10 for admission of live steam, connects the port 11 with the vexhaust port 13 leading to the exhaust pipe-14,'

while when the valve is shifted into its other position to uncover the port 11 for the admission of live steam, said cavity 12 connects the port .10

with the exhaust port 13.

The valve 6 is of the usual steam-actuated type, it being connected tov and operated by a differential piston structure comprising the two piston elements 15, 16. The `action of the steam pressure in the steam chest 7 on the differential piston normally tends to move the differentialV piston into its right hand 4position thereby connecting the port 10 with 'the exhaust and admitting steam to the port 11, in which case the power piston 3 would be moved-upwardly.

To bring the valve 6 into the position shown in Fig. 1 live steam is admitted to the cylinder space 17 at the right hand side of the larger piston ele- .ment 16 thereby substantially balancing the pressure against the left `hand side of said piston element, the result `being that the pressure oi the steam against the smaller piston element'15 will shift the valve into the position shown in Fig. 1 thereby admitting steam to the upper end of the cylinder 1.v K The control of the admission of steam to the chamber 17 is through the 'usual reversing valve 18 which is actuated by the piston 3. This reversing valve operates in a steam chest 19 which is supplied with live steam through the steam passage 20. When the reversing valve is in its` raised positionfthe cylinder space 17 has communication with the steam chest 19 through the port 21, the admission of steam to the cylinder space 17 causing the differential piston 15, 16 and valve 6 to take the position shown in 1. Whenv the reversing valve 18 is in its lowered position the inlet port 21 is closed and the cylinder space 17 is connected with the exhaustport 13 through the ports 22, 23 and the exhaust cavity 24.

The valve 18 is reversedin the usual way by the movement of the power piston 3 through the medium of the reversing plate 25 which co-operates with the reversing rod 26 secured to the valve 18, said reversing rodextendinginto anr axial recess formed in the lpiston rod 5 and having the shoulders 27, l28 thereon with which the plate 25 engages near the ends of the stroke of the power `piston 3. As the power. piston 3 nears the lower end of its stroke the reversing plate 25 engages the shoulder 28 and draws the valve into the position shown in the drawing which will again reverse the power piston 3.

As stated above this type of valve mechanism is such as is commonly employed in certain types of steam 4engines and is one which admits live steamto the cylinder during the entire stroke of the-power piston, and in which cut-off comes at the end of the stroke and there is no expansion of steam. This arrangement has the advantage that it ensures that the piston will always start when Vsupplied with live steam, for with the cut-off at the end of the stroke the port leading to one or the other end of the cylinder will always be open when steam is again admitted, regardless of the position in which the power piston may be when the engine stops.

It will be .noted that with this valve mechanism vthe movement of the steam valve in one direction is accomplished by admission of live steam to the cylinderv space 17 and thermovement in the opposite direction is accomplished by exhausting the steam from said cylinder space 17.

The admissionof steam to the steam cylinder 2 is controlled by a steam valve 29 which is similar in all respects to the valve 6, said valve operating in a steam chest 30 which communicates with the passage 8 and said steam cylinder 2 having the ports 31 and 32 leading from the steam chest 30 to the opposite ends thereof.

33 is an exhaustport which is brought into communication with eitherl of the ports 31 or 32 through an exhaust cavity 94 of the valve 29 depending upon the position of the valve. This valve 29 is also a steam operated valve and it rhas associated therewith the diierential piston mechanism comprising the piston elements 34 and 35,

Thev

reversing valve 36 which is similarv in construction Ato the reversing valve'18, said valve having the reversing rod 37 thereon which extends into an axial bore in the piston rod 5 and is actuated to reverse the valve 36 bythe reversing plate 38 ing plate 3K8 will engage the. shoulder 40 and will draw the reversing valve 36 downwardly into'the position shown in Fig.v 1.. This will cutoff the inlet port 41 and will connect the port 42 withthe exhaust port'43 through the exhaust cavity 44. When the reversing valve is inthis position the pressure of the live steam in the steam chest 30 onthe differentialpistons34, 35 holds said pistons and the valve 29 in the position shown in Fig. 1.

When the power piston 4 reaches the upper` end of its stroke it shifts the reversing valve 36 upwardly to uncover the inlet port 41. In order to effect the reversal of the power piston 4, however, it is necessary to admit live steam to the cylinder space at the right of the differential pist0n element 35 and the admission of i such live 'mately midway of the length thereof.

connections 52 and 53 each have a vcheck valve 58 therein, each check valve permitting free flow steam is controlled by the movement of the power piston3. f f

Live steam is admitted to the steam chest 66 for the valve 36 through a passage 45 and pipe connection 46 which leads to a vvalve device 47. This valve device has a cylinder chamber in which Yoperate two pistonvalves 48 land 49 of different valves will move as a unit, but if steam pressure is admitted to the space 67 between the piston valves then they are permitted to separate, the reason for which will be more fully hereinafter set forth. l f

The valve casing is provided with an inlet port 50 communicating with an inlet pipe v51,l said pipe `51 having two branches 52 and 53 thatlead to the cylinder 1, the branch 52 communicating lwith the cylinder at the port 54 near the upper end thereof and the pipe 53 communicating with the cylinder lat the port 55 near the lower end thereof. The upper end of the cylinder chamber of the valve casing 47 is connected by a pipe 56 toV a port 57 leading into the cylinder 1 approxi- The pipe of steam through its pipe connection to the inlet pipe 51 but preventing flow in the opposite direction. f Y

As the power piston 3 moves downwardly and uncovers the port 54 live steam will be admitted to the pipe connection 52 and through the inlet pipe 51 and port 50 to-the lower end of the cylinder chamber in the valve casing 47, the check valve 58 in the pipe connection 53 preventing flow of steam from the pipe connection 52 to the pipe connecti0n53. At this time the ports 57 and 55 are on the exhaust side ofthe powerV piston 3. The admission of the live steam through the pipe connection 52` will y'operate to raise the piston valves 48, 49 thereby uncovering the port 59 and allowing the live steam suppliedl through the pipe connections 52 to ow through' the pipe connection 46 and passage 45 into the steam chest 66 of the reversing 'valve 36.

The same thing occurs when the power piston 3 is moving upwardly and has'uncovered the port 55, the live steam then being admitted to the piston valve and to the connection 46 and passage 45 through the pipe connection 53, the check valve 58 in the pipe connection 52'preventing flow of steam from pipe connection-53 to pipe connection 52. These check valves 58 thus prevent bypassing of steam through either pipe connection 52, 53 when steam is admitted through the other connection.

It will be understood that the power piston 4 reverses itself automatically when it reaches the bottom of its stroke. When said power piston 4 nears the upper end of its stroke it raises the reversing valve 36 `but there will Abe no shifting vof the steam valve 29 until the power piston 3 reaches a predetermined position, ywhich may either be that in which it uncovers the port 54 on vthe downward stroke or uncovers the port 55 I'on the upward stroke, thus admitting live steam to the uncovered port. As soonvas this happens then the differential piston valve 48, 49 will be actuated as above'described and live steamfwill be admitted 5to the steamtchest'of the valve'f36 thereby to "operate :the differentialpiston 34, `35

Qandthus reverse the power piston 4.' The power piston 3, therefore, providesfduring Veach stroke thereof ani opportunity for 'reversing the-va1ve S29 provided fthe -power piston 4fhas previously reached the upper-end of its stroke and has raised the reversing valve 36. The construction of the valve-'mechanism 47, however, issuch that this lopportunity will be removed after "the power pisl ton` 3 has moved through apredetermined portion of 'lits stroke! and. ifi: the reversal of .ther piston 4 doe'sfinot :occur while-ths opportunity lasts then said piston' 4` cannotfbe 'reversed until the piston Bloffers another` opportunity for 'such reversal.

lIhis opportunityfor-reversing the power piston. -4 at the upper end of its stroke yoccurs while the power piston3` ismoving fromeither the port 54 vorthe port 55 to the port 57. Assuming .that the power piston 3 is moving'downwardly, then when it uncovers the port 54the differential piston valve 48, 49 is shifted as above described to allow steam to be admitted tol the steam chest of the valve 36 thereby givingtheopportunity` for reversal of the valve v29 provided the power piston 4 has reached the upperfend of its stroke."

' When the power piston -3 has moved downwardly far enough` to uncover' the port`571 then live steam will be admitted through the pipe connection 56 to the upperend of `Ithe cylinder chamber in the piston valve casingr47. Since the upper pistonY member 49 is vlarger than the piston member 48the admission' of .steam to the upper end of the cylinder chamber will force thedifferential piston downwardly into the position shown in Fig. 2 and inthis position the port 59 with which vthe pipe connection 461communicates'willbe in communication withl a port 60 leading to a pipe connection 61 that leads tothe 'steamspace 62 atthe upper end ofthe cylinder 2.

The operation of the devicevis as follows. Supf pose the engine to be just starting-fromV rest. 'Ihe power pistons 3 and 4 may be in-any position and may start in either direction when steam is rst turned on; `Assuming, for` example, `that the power piston 3 has just been reversed at'the upper end of its stroke then when'the steam' is turned on the steam valve 6 willbe in the position shown in Fig. 1 and steam `will be admitted Itov the upper end of the cylinder 1 so that the powerpiston 3 vis moving downwardly. 'If the power'piston 4 and itsvvalve *arez positioned so that said piston rstarts to move `downwardly'then it vwill reverse itself at the bottom end Vof its'stroke and start upwardly. When the power. piston 4"nears the y topl of its strokeit raises'the reversing valver 36 thus uncovering the port 4l andthe parts vmust remain in this positionfun'til live steam has been admitted to the steam chest of the valve 36 through `the movement of the power piston 3. As soon as the piston 3 uncovers either the vport 54 when movingdownwardly or the port 55 when lmoving upwardly the differential valve 48, 49 will `3 passes ythe :port 57` then"the opportunity for reversalr of the power pistn 4- is removed,` for when the power piston '3 over-travels the port 57 then live steam isfadmitted ythrough the pipe connection 56 into the upper'endof the piston `-valve` chamber 47 and both` differential pistons sure -wouldresultfin the valve 29 being moved f 4:8,v 49 'movegdownwardlythus cuttingoir, the i, supply of live steamtoythe steamchest 66 ilof fthe 'valve 36 throughtherpipe` connection 46;,- If

after. this Voccurs the; power piston,.f4 ;reaches,.- the upper end .of its ,stroke'andis readyqto reverse `there will be no steam to Icause i"e,versa-loi?'the valve 29 and said powerpiston4 musti'therefore,

:wait in itsraised position until live steamiiis again admitted to thesteamchestofftheivalve 3 6. As `soon as the Vdifferential Vpiston valves .48, l49 have been moveddownwardlyinto theposition .shown in :Figi: 2 the steam g chest of; the iva1ve36 steam. chestl `66 when the jpower piston 3 overtravelsthe port ,54,1wi1lpthus exhaustedv thus .removing the opportunity for reversing the valve From the above it willfbev seen that ari-@opportunity is given `thepower piston 4l to reverse while the powerv piston 3*,moves-downwardly from the port 54 to the port 57 and thatthe opportunity is removed as soonas4` said power piston 3 passes by the port57, 1 It will also be seen. that 'another opportunity for the power ypiston 4 to reverse is againpresented-.while the powerpis- Vton 3 is moving upwardly from the port 55 to the port 57and that whensaid power piston isfmoved upwardly beyondthe port 57 rsuch opportunityis again removed.. f

The opportunity, ,thereforeffor thepower piston 4itovreverseiatfthefupper Vend of its r stroke -is Agiverrafter thepowex'jpiston 3 leaves `either end of itsstroke and while. itis moving from-near either end `'to about the center of the ,cylinder 1,

and hence under nrirmalxzonditions A the reversing of thepower piston 4 atthe upper endo! the stroke mustoccurrwhilethe pistonA 31s :moving through a predetermined portionVV ofits zstroke in one lor the other direction. Y Y

Ther construction above described not onlygpro- `vides ffor ,the reversalof vthe power piston :4 at

the upper end of its` stroke :but it ensures `that i the power piston 4 will make ',itscomplete downward strokebeforeagain reversing-...morder to vsecure;thisfresult it is necessary-.that-the valve 29 should be maintained lnits left hand posiytion during the entiredownward vstroke of the power piston. If it be assumed that the power piston y4 has reversed atv the upper end of its stroke before the power. piston 3` hasuncovered the port- 57 then asl soon as v,sadwprt has been uncovered the differential piston valves. 48, 49,y will be `movedinto'the position shown in Fig. 2. vvThis will place the pipeconnections 61 and 46 in communication so' that 'live steam. which is ,being admitted to the upper end of the-cylinder-Z Vmay pass throughv theconnections 61,- 46-and-into the 'steam chestf66 thereby fmaintainingythe necessary pressure therein tohold the valve 29-.in its left handposition,and-avoiding the, possibility that such pressure might be lost due tojleakage or otherwise before the power piston 4vlias Icompleted'its downward stroke, which loss 'of ypresinto the position shown inFig. 1 and thusrelversing the power piston 4 -before it .had completed its downward stroke. i y' i When the live steam yis passing through the pipe connection 6l into thesteam space 67 of the diierential valve the steam pressure on the power piston .3. l.

l.underface ofthe 'piston' :valve 49 tends to raise it but as the piston valve 49 is separate from the pistonyvalve48 thissteam pressure merely raises the piston valve 49 and holds the piston 48in its lowered `position andthe communication be- Atweenthe ports 59 and,60.is thus preserved. This piston vvalve structure, therefore, also functions as a pressure-maintaining means for maintaining relative speeds-.ofthe pistons, such relativepositions of the; pistons being determined by the position of the ports 54, 55 and 57. With this improvement, therefore, itis impossible for, the ytwo `power pistons to reverse.` simultaneously and they are; always-v maintained in out-Of-stepprelation-The invention also provides means whereby the power piston 4 is given an opportunity for Va'shortintervalof time only during eachv stroke pfthepowerpiston3 to Yreverse and toget into the predetermined out-ofstep relation with-said The invention further, ensures that each piston .will make a full lstroke in either direction before reversingV land it prevents any undesired reversal ofthepower piston 4l during its-downr` ward stroke-by providing a pressure-maintainfeature for maintainingv the pressurevgin `the chamber 66 during the full downward stroke of Said Power-piston ,4.Y Y

-In,-Fig, 3 I, have illustrated'mv. inventionas :it might be applied` to a duplex engine in which the cylinders arecompounded.- In said figure 71 `represents the highvpressure cylinder having the high pressure piston 72 thereinand 73 is the low pressurecylinder; having Ithe low pressure .piston 74 therein., Y

The valve .mechanism for controlling the sup` ya steam valve operating a steam chest 7 and ,controlledjbyA-two ydiiferential ypistons 15;v 16, the

operation vof which in turn is controlled by thev reversing valve 18 that is actuated by the reversing plate 25 carried by thepiston 72. ,Y

The valve-.mechanism controlling the admission ofsteam to the low pressure cylinder-73 'is also the same asthat shown in Fig.v l for controlling l.the-supply -of steamtofthecylinder 2 and comprises a steam valve 29 operating in a steam chest 30 `and operated by differential pistons 34,35, 'the operationA of which in turnis controlled by a reversingvalve 36, vthe position of which is reversed ateach end of the stroke of the low pressure piston through the operation of a reversing plate 38 and reversing rod 37.

5 SinceJFigfS shows acompound engine the live steam willbe admitted to the steam chest 7 only andthe steam chest 30 is connected through a passage 75 to a receiver chamber 76 into which .the steaml fromv `the -highpressure cylinder 71 .is exhausted as shown in the above-mentioned Pat- Ient No. 1,962,986. .Thelive steam for the high pressure .cylinder is supplied through a supply pipe 77 which communicates with the steam chest 7 throughthepassage 78. e The differentialvalve mechanism which is controlled by the high pressure piston 72l and which cooperates with the lowv pressure' piston-74 to ensure reversal of the latter at the upperV end of the stroke is shown in section in Fig. lland it comprises a valvecasing 79 in which operates two differential piston valve members 80, 81 which are similar to the piston valve members 48, 49. The

high pressure cylinder 71 has the port 82fwhich is connected by a pipefconnection 83 to the port 84 near the lower end of ,.the valve casing 79.A Said high pressure cylinder has another port 85 communicating by a pipe connection 86 with v.a

port 87 near the upper end ofA the piston valve casing 79. The steam chest 66 in which the valve 36 operates is connected by a pipe connection 88 to a port 89` leading to the .cylinder chamber of the piston valvestructure 79.` VThis piston valve structure has another port 90 corresponding to the port 60 of Fig.2 and which communicates with a pipe connection 91 to the clearance space 92 at low the live steam to flow through the pipe con-,

nection 88 into the reversing valverchamber 66. If atV this time-the low pressure piston 74 has reaohedthe upper end of its stroke then it will have raised the reversing valve36 by the action of the reversing plate 38. -The raising of the reversing valve into its upper position will uncover the port 41 so that the live steam from the reversing valve chamber 66 may be delivered to the chamber containing the differential pistons 34,35. '.Ihis will shift the differential pistons to the left thereby causing reversal of the low pressure piston. The construction, therefore, is similar to that shown in Fig'. 1 in that during a predetermined portion of the travel of the'hirgh pressure piston 72 it provides the opportunity for the reversal of the low pressure piston provided said low `pressure piston has reached the upper end of its stroke.

As ythe high pressure piston continues its downward movement and uncovers the port 85 -then live steam will be admitted through the pipe con-- nection 86.to the upper. end of the valve casing '79 and because of the differential nature of the piston valves 80, 81 said piston valves will be forced downwardly into ltheposition shown in Fig. 4. i 1 f If the low pressure pistonf74 hasreached the upper end of its stroke and raised the reversing valve 36 prior tothe overrunning of the port 85 by the high pressurepiston 72 then when the differential piston valve 80, v81 .has been moved into the position shown in Figf4 the pipe connections 88 and 91 will be brought -into Icommunication and steam under yreceiver pressure will flow through the pipe. connections 91, 88 so as to maintain the receiverpressurein'the reversing-valve `chamber 66, such receiver pressure maintaining the differential piston 34, 35 in-its left hand position during the full downward stroke of the low pressure piston 74'. If, however, the low pressure piston hasnot reached the upper end of its stroke and, therefore, has not raised the reversing valve 36 before the high pressure piston 72 overruns the port 85, then the bringing of the pipe connections-88 and 91 into communic ation'bytl-ie4 shifting of the differential piston valve 80,` 8l into the position shown in Fig.v 4,.will connect the `reversing-valve rchamber 66 with'the exhaust throughthepipe connections 88,91 and the receiver pressure Ywhich was admitted-to the reversing-valvechamber will bey exhausted thereby removing the opportunitylfor the reversal of the lowpressure piston.

The .apparatus shownin Fig. Y'3, therefore, operates `'as described with reference to Fig. 1v in `that duringl a. predetermined `portion of .the travel of the high pressure ipiston `itprovides the opportunity for the reversal of the low pressure piston, and if such reversal does not' take place vduring the movementlof the high pressure piston through such predetermined portionof its travel, then, the

opportunity is takenaway and the low pressure.r piston cannot be reversed until thel high pressure piston again l provides.. such opportunity'. for` reversal during a succeeding stroke. The'particular portion of the stroke .ofthe high .pressure piston vduring which such opportunity for reversal of the low pressure piston is offered will depend upon the location'of the ports 82, 85. p

Inthe construction shown in Fig. 3 such opportunity for reversal of the low'pressurepiston will kbe presented during each down stroke only of the high pressure piston `.'12 but byy providing the requisite number of ports and proper connections the opportunity for'reversal might be offered yduring each stroke ofV thehigh `pressure piston.

While I` have illustrated herein two selected embodiments of my, invention kI 'wish itfunderstood that the constructional features maybe varied in many ways'without departingfrom the inven-v tion'as expressed in th'e'appended claims. I claim:

1. A duplex steam engine havingwtwo steamU cylinders, a power piston in each cylinder, a valve for reversing one of the pistons, valve-operating means rendered operative jointly by said piston when it reaches 'one end of Aitsstroke and by the movement of .the otherfpiston' duringits travel in eitherY direction.

2. A duplex -steam'fengine having'two st'eanr cylinders, a power pstonin each cylinder, said:

pistons beingcapable of movement independently of each other and'onev of the pistons being a selfreversing piston, a valve for reversing the other piston, valve-operating means rendered operative jointly by saidother piston when it reaches one end of its stroke and bythe movement of .the selfreversing piston during a predetermined portion of its travel in either direction for reversing said i other piston at said endof the stroke, said valveoperating means being also rendered operative toY reverse said otherpiston at the "opposite end of its stroke solely by said otherv piston itself.

3. A duplex steam engine having two steam` cylinders, a powerr piston in Aeach cylinder, said pistons being capable of movement independently of eachother and one ofthe pistons being a yselfreversing piston, a valve for reversing the other piston, means rendered operative byv the vother piston as it reaches oneend of its stroke tof actuate said lvalve and meanscooperating with the first-named means to cause the valve to be actua. ated jointly by said other piston when" it reachesv the oppositeend of its stroke andbyfthe movement of the self-reversing piston during apredetermined portion of. its travel'in eithe'rdirection.'v

k4. A duplexrsteam enginehaving two steam cylinders, a power piston in each cylinder, saidA pistons, being capable o f movement independently of each other and one of said pistons "beinglalself-reversing piston, a steam-actuated valvedor`r reversing the other piston, means actuated by fthe'l other piston at one end of its stroke forfrendering said valve operative,1and -means controlled bythe movement of the'selfr-reversing piston during its travel in eitherdirection and co-opewrating with said valve-actuating means to render f lthe valve operative at the opposite endjof the stroke of said other piston.- g j, j

5.*A duplex steamengine having` tlv'vosteam" cylinders, a power pistonjinieach cylinder, 'said power pistons being capableV of` movement' inde-V pendently of each otherand one of said` power pistons being a' self-'reversing` piston, a steamactuated valveV for'reversing the other piston4 at each end of its stroke, means rendered operative by said other piston" at oneend of its lstroke' to cause operation of said valve,4 and means cooperating With said last-namedmeans and controlled by the self-reversing jpiston during apredetermined portion only of'its travel to render said valve-actuating means operative at the opposite end of the strokeof said other piston.`

6. A duplex steam engine having twofsteam cylinders, a powerpiston ineach cylinder, said pistons being capable ofrmovement independently of each other and one ot' said pistonsbeing a self -reversing piston, a steam-actuatedr valve. for` reversingithe other piston at each end of its stroke;

means rendered operative by said other' piston at one ,end of its strokento cause operation of said valve, and means co-operating'with said lastf named means and controlled by the self-revers` ing piston during a predetermined portion only of its-travel to admit ,steamlto and thereby actuate said valve at' the opposite end of thestrokeof saidother piston. l a

7. A duplex steam engine having two steam cylinders, a power piston in each-cylinder, said pistons being capable of rmovement independently` of each other and one of said pistons being aj self-reversing piston, a 'steam-actuatedvalve: forV l reversing the other piston'at each end` of its stroke, means rendered ,operative by'said other piston at one end of its stroke to' cause operation of said valve, and means co-operating with said last-named means and controlled by the self-reversing piston during a `predetermined'portion only of its travel to admit steam to and thereby" actuate-said valve atthe opposite end ofthe stroke of said other piston, and to exhaust the f steam from said valve during another portion of each end ofgits stroke, and means `cooperating 65 with `said reversing valve andcontrolled by the' self-reversing piston during a predetermined por'- tion Aonly of its travel in either direction to admit steam tosaid steam-actuated valve.'

9. A duplex steam engine vhaving vtwo steam cylinders, a power .piston in each cylinder, said pistons being capable of movement independent-y ly of each other Iand one of the pistonsbeinga Vself-reversing piston, a steam-actuated valve for reversing the other piston at eachv endof -its stroke, 4a reversing valve for said ysteam-actuated valve, meansto'actuate the reversing valve by the movementof said other pistonI as it approaches each end of its strokeyand means co-'operating with said reversing valve and controlled by the 1 self-reversing piston during a predetermined portion` only of its travel in either direction to admit steam to said steam-actuated valve and to exhaust steam therefrom during another portion of y the travel of said self-reversing piston.

10.,A` duplex steam engine havingtwo steamc ylinc'lera-av power pistonfin each cylinder, `said'-l pistons being'I capable of movement independently of eachother and one of the; pistons being aselfvreversing piston, 'alsteam-actuated valve fforre t t versing theother piston at each endoi its st rctike,

aV reversing valve controlling admission of steamV to and' its exhaust'from said steam-aotuated-valve, f

means `'controlled by thev self-reversingpistonduring a predetermined portion only ofits travel to admit steamto the reversing valve andduring another portion 'of` its travel inthe same direction to exhaust vsteam therefrom, and means actuated by said otherpiston at each end of its stroke a steam-actuated piston for operatingY said valve,- areversing valve controlling the delivery of steam to said piston for actuating the latter, means actuated by saidother piston at each end of its stroke,

to reverse lthe position of the reversing valve, and

means controlled by the self -reversing piston dur-,t inga predetermined vportion only ofv its travelto admit steamV to the reversing valve, said last-` named means being operativetov maintainathe steam pressureon theAvalve-actuating piston dur-v ing the full stroke of said other power-piston.

` 12. A duplex steam engine having two "steam cylinders'a powerv piston in each cylinder, said power pistons-being' capable of movement independentlyof eahvotherpandone of said pistons being a self-reversing piston, a valve for-reversing theother vpower'piston at each end of its stroke, a steam-'actuated piston for operatingy said valve, a reversing valve controlling thedelivery of steam to said latter piston for actuating it, means actuated by said other power piston at eachend of its stroke tore/verse the position of' the reversing valve, and means controlled bythe self-reversing power piston during apredetermined portion only of its travel to admit steam to the reversing valve, said last-namedmeans being operative to maintain the steam` pressure :onA the valve-actuating piston during the full stroke of said other powerl piston in case said `other-pbzivver piston has completed its stroke before thel self-reversing piston has completedthe rpredetermined portion of its travel and to exhaust the steam from saidA revers-` ing valve in case said vother power piston is not reversed before the completion of said predetermined portion'of the travelof the self-reversingv piston. 1 1" j 1 j 13. A duplex steam engine having twovsteam cylinders, ya power piston in' each cylinder, a steam-actuated valve-for reversing one of said pistons, means controlled partly by the other pistonduring a predetermined portion of its stroke and partly by the mst-named` pistonfor supplying steam to actuate said valvei-n case the firstnamed pistonhas reached thev end of its stroke during the movement of saidother piston through said predetermined portion of its stroke, which means are inoperative to supply steam in case the first-named piston has not reached the end of its stroke while the said other piston is moving through said predetermined portion of its stroke.

14. A duplex steam engine having two steam cylinders, a power piston in each cylinder, said pistons being capable of movement independently of each other and one of said pistons being a self-reversing piston, a steam-actuated valve to reverse the other power piston, a reversing-valve chamber, means controlled by the self-reversing power piston to supply steam to the reversingvalve chamber during a predetermined portion of the stroke of said self-reversing power piston, and a reversing valve operating in said chamber and actuated by said other power piston for controlling the admission of steam from said chamthrough the predetermined portion of its stroke and to exhaust the steam from said chamber in case said other power piston does not reach the end of its stroke while the self-reversing piston is moving through said predetermined portion of its stroke.

lMYRON W. DOLE. 

